This is a final report on an experimental research program to characterize the optoelectronic properties of very heavily sulfur doped silicon (also known as Black Silicon) in close collaboration with scientists at US Army Benet Labs, Harvard, and the Army Research Laboratories. Materials and devices will be prepared at Harvard. The thrusts of the proposed work were: i) to elucidate the origin of excess infrared absorption and to determine how this absorption contributes to photoresponse, and ii) to measure the transport properties of photoexcited charge carriers. By analyzing the photoconductivity and photoresponse of coplanar and diode devices we were able to set limits on the mobility-lifetime product of sulfur-hyperdoped material. We have proposed an excitation and charge separation mechanism that is consistent with all data.